Tongues were a sign to Jews, meaning Jews were present (1 Cor. 14:21-22).

1 Cor. 12:7 and 1 Pet. 4:10 say that all gifts are for serving others, for the common good. There is no suggestion that tongues or any other gift was for private use. 1 Cor. 14:4 says that tongues would edify the individual and that is quite understandable. It would probably be even more edifying to heal someone, however, personal edification was not the intended purpose of any gift. Tongues, with interpretation, were given to build up the church, not the individual, as the following show:

1 Cor. 12:7 – “… the manifestation of the Spirit is given for the common good…”
1 Pet. 4:10 – “… each one should use whatever gift he has received to serve others…”
1 Cor. 14:5 – “… so that the church may be edified.” (Note 1 Pet. 4:10)
1 Cor. 14:6 – “… [without interpretation] what good will I be to you?”
1 Cor. 14:7 – “… [without interpretation] how will anyone know…?”
1 Cor. 14:8 – “… [without interpretation] who will get ready…?”
1 Cor. 14:9 – “… [without interpretation] how will anyone know…?”
1 Cor. 14:11 – “… If I do not grasp the meaning of what someone is saying…”
1 Cor. 14:12 – “… try to excel in gifts that build up the church.”
1 Cor. 14:16 – “… how can one who does not understand say ‘amen’?”
1 Cor. 14:16 – “… he does not know what you are saying.”
1 Cor. 14:17 – “… the other man is not edified.”
1 Cor. 14:19 – “… to instruct others…”
1 Cor. 14:26 – “… all things must be done for the strengthening of the church.”
1 Cor. 14:27 – “… if anyone speaks in a tongue … someone must interpret.”
(Taken from All About Speaking In Tongues by Fernand LeGrand)

These verses all point to the public use of tongues with interpretation for building up the church. There is not a single verse that supports the use of tongues for private prayer.

A passage said to support tongues as a private prayer language is 1 Cor. 14:13-17. These verses talk about praying in tongues but interpretation is called for so that others can say “Amen” so clearly this passage describes a public prayer setting and has nothing at all to do with private prayer.

1 Cor. 14:2 is also used in the attempt to prove that tongues is a private prayer language. It says, “For anyone who speaks in a tongue does not speak to men but to God. Indeed, no one understands him; he utters mysteries with his spirit”. Obviously, this verse cannot support private prayer either as it says, “no one understands him”, telling us that it’s a public setting. Three other points about this verse are –

i) Many believe that the “mysteries” of 1 Cor. 14:2 are angelic languages but this comes from a misinterpretation of 1 Cor. 13:1-3 in which Paul uses exaggerated speech to show that love is greater than all. He is not saying that he could do the impossible and fathom all mysteries or have all knowledge etc but even if he could, yet didn’t have love, then he had nothing. Likewise, he is not saying that anyone could speak in the tongues of angels; that too is exaggerated language.

ii) By itself, 1 Cor. 14:2 makes absolutely no sense as it says that no one, except God, ever understood anyone who spoke in tongues. Obviously, this is wrong because tongues were understood (Acts 2:8). To make sense of this verse we need to look at v.28 which is also talking about speaking to God. It says, “If there is no interpreter, the speaker should keep quiet in the church and speak to himself and God”. So, if we consider v.2 in the light of v.28 we see it is saying that, without an interpreter, the speaker should keep quiet and talk to God as no one understands him. Again, this is a public setting and, without interpretation, the speaker would have been uttering mysteries in the same way that any foreign language is a mystery to us, unless interpreted.

iii) The KJV has helped to confuse this issue by adding “unknown” to the text implying that some tongues were unknown languages. However, all tongues from God were known, human languages just as 1 Cor. 14:10 tells us: “There are doubtless many different languages in the world, and none is without meaning”.

Finally, a careful study shows that every verse on tongues, whether about prayer or otherwise, is in the context of a public setting with interpretation called for every time. Not a single verse speaks of the private use of tongues. This is because tongues was a sign of judgement to unbelieving Jews and, once that purpose had been served, speaking in tongues ceased. See “Speaking In Tongues – A Sign” at –http://www.christianissues.biz/pdf-bin/blogarticles/tonguesandasign.pdf

The following books on the cessation of Tongues, Prophecy and Knowledge are free to download.